Scott Taylor, who is playing on a sponsor's exemption, had a round that included an ace and a 70-foot birdie putt. He shot a 3-under 69 and is tied for fourth place with Kris Mikkelsen, Michael Harris, Matt Bettencourt and Chris Carnahan.
Heavy winds swirled throughout the round, allowing only 17 players to break par in the opening round.
Johnson flew out of the gate on Thursday with four birdies in a row to open his round. He parred his next 11 holes before a birdie at No. 16.
Johnson's lone mistake came at the 17th when he tried to keep the water out of play off the tee. His ball landed in a bunker behind the green and he blasted out to 40 feet. Johnson three-putted for a double bogey, but he birdied 18 to grab a share of the lead.
'Whenever you get off to a start like that, you want to try to think you are still at even-par and not 4 under,' said Johnson, a three-time winner on the Canadian Tour. 'It's like being at the casino and winning your first four hands. You want to be able to put some of it away.'
Riskam mixed six birdies and two bogeys in his opening round.
Nosler, a semi-finalist in the 2001 U.S. Amateur Championship, played the back nine first on Thursday at Brookside Country Club. He broke out with four consecutive birdies, but dropped a shot at No. 18. Nosler birdied the fourth for his only birdie on his second nine.
Brennan Webb, who holed out from 148 yards out for an eagle at 15, carded a 2-under 70 and is tied for ninth place with Tom Johnson.
Ryan Longwell, the kicker for the Green Bay Packers, shot a 9-over 81 and is part of a group tied for 142nd place.